The present invention relates to a facsimile apparatus which achieves a considerable transmission rate by transmitting selected one of video data associated with a document which has been provided by scanning the document in a particular direction higher in compression ratio than the other direction or directions.
Traditionally, in a transmission mode operation of a facsimile apparatus, images on a document are scanned with a shorter dimension, or widthwise direction, of the document defining a main scan direction and a longer dimension, or longitudinal direction, defining a subscan direction, so that a video signal continuous along each main scanning line is transmitted after code compression. Documents are sometimes ruled parallel to the lengthwise direction thereof, that is, recorded with many patterns which are rather continuous in the lengthwise direction that in the widthwise direction. A code compression ratio attainable with such a kind of documents is not very large because a black pixel with a short run-length appears frequently in a video signal associated with each main scan line. Stated another way, it is rather favorable from the higher compression ratio standpoint to code compress a video signal which is continuous in a direction parallel to the lengthwise direction.
However, a prior art facsimile apparatus is designed to code compress video signals solely in the main scan direction, i.e. widthwise direction of a document, so that the attainable compression ratio is limited when it comes to transmission of a document carrying a lot of lengthwisely continous patterns. The limited compression ratio is reflected by greater time consumption for video data transmission.